Overview
On May 19, 2025, a critical vulnerability was disclosed in the Gardener Kubernetes cluster management platform. Identified as CVE-2025-47283, the flaw permits privilege escalation by bypassing project secret validation, potentially allowing a project administrator to gain unauthorized access to the seed cluster(s) responsible for managing shoot clusters.
This vulnerability is tracked under GHSA-3hw7-qj9h-r835 and has been rated as Critical with a CVSS v3.0 base score of 9.9.
Technical Details
The vulnerability stems from improper input validation, categorized under CWE-20: Improper Input Validation. This means that user-supplied data is not properly checked before being processed, allowing potentially malicious input to influence system behavior.
In the context of Gardener, an administrative user within a project could manipulate secrets associated with their cluster to influence the behavior of the gardenlet component running on the seed cluster. This manipulation enables them to elevate privileges and execute operations outside their intended scope.
Impact
This flaw impacts all Gardener installations regardless of the public cloud provider used for the seed or shoot clusters. Exploitation could allow:
- Unauthorized control over seed clusters
- Compromise of other tenant clusters
- Loss of confidentiality, integrity, and availability within the Kubernetes management infrastructure
The vulnerability has a Changed Scope in the CVSS vector, indicating that an attacker’s access could impact components beyond the initially vulnerable system.
Affected Versions
The following versions of gardener/gardener are affected:
- All versions prior to 1.116.4
- Versions 1.117.0 through 1.117.4
- Versions 1.118.0 through 1.118.1
Mitigation
Users are strongly advised to upgrade to one of the following patched versions:
- 1.116.4
- 1.117.5
- 1.118.2
- 1.119.0 or later
Upgrading ensures that project secret validation is enforced correctly, preventing unauthorized privilege escalation within the system.
Understanding the Terms
Gardener is an open-source project developed by SAP that enables the automated management of Kubernetes clusters at scale. It introduces the concept of shoot clusters (end-user Kubernetes clusters) and seed clusters (infrastructure clusters that host shoot clusters).
CVSS (Common Vulnerability Scoring System) provides a numerical score to indicate the severity of a vulnerability. A score of 9.9 indicates an extremely high risk, especially when no user interaction is required and the attack can be performed remotely.
CWE-20 represents a category of vulnerabilities arising from improper input validation, a common flaw that can lead to injection, escalation, or arbitrary code execution.
Conclusion
CVE-2025-47283 highlights the importance of strict input validation and the risks posed by misconfigured secrets in Kubernetes management platforms. Organizations using Gardener should patch immediately and review their cluster access policies to ensure secure multi-tenancy.
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